Communication skills in deaf and hearing children will be investigated using referential communication tasks, tests of grammatical knowledge of ASL and English, and a communication skills inventory administered to parents, teachers, or other persons in a position to judge the children's ability to communicate to various kinds of persons in different situations using one or another means or modality. Training studies and longitudinal follow-up studies will be conducted to evaluate specific deficiencies or developmental lags observed in deaf children's performances. Special attention will be given to the role of the listener in referential communication and listeners' ability to respond appropriately to ambiguous messages and messages with irrelevant information.